Conventionally, an interdental brush has been used to remove any food debris or dental plaque and the like in a gap between teeth which cannot be removed by a normal toothbrush or to massage gum in an interdentium part (e.g., Patent Document 1 and the like). In addition, since a large number of anaerobic bacteria hide in a gap region between teeth, use of a drug when an interdental brush is used is effective, and a drug for a mouth cavity such as a dentifrice is often used by being applied to bristles when an interdental brush is used.
While such an interdental brush, however, is often used outside of home, in such a case, it is inconvenient to carry both an interdental brush and a drug bottle in terms of portability. Hence, a drug-containing interdental brush in which an interdental brush is integrally formed with a drug bottle has been developed (e.g., Patent Document 2 and the like).